1. Technical Field
The present invention relates generally to motor vehicle assembly and more particularly to electrical testing of a motor vehicle chassis before mating of a body to the chassis.
2. Description of the Problem
The electrical system of a motor vehicle such as a school bus can be difficult to troubleshoot on the assembly line. In the case of school busses, the bus body is normally assembled on one assembly line and the chassis on another. Body and chassis are then mated. The procedure can make it difficult and time consuming to access electrical devices such as wiring connectors to troubleshoot an electrical problem discovered after mating.
The electrical connections between the chassis and the body are often the ideal location to start when troubleshooting a bus electrical problem. This serves to isolate the problem as a body or chassis issue. However, opening one of the multi-terminal connections between body and chassis to test a circuit can create other problems which mask the root cause of the problem. In addition, using a test light or jumper wire connected to battery negative (i.e. ground) or battery positive can cause damage to the vehicle electrical system, especially when a body systems computer is used to control lights, doors, etc. Probing the wrong connector cavity can result in unexpected operation or damage to electrical system components. If the vehicle has a body systems computer, using a voltmeter to perform this troubleshooting can also result in an incorrect diagnosis due to power MOSFET leakage current. Additionally, the wiring in the school bus body is often limited to a small number of vehicles due to State and local requirements. This leads to still further difficulties in troubleshooting.